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Merge branch 'trace-add-tracepoint-for-tcp_sendmsg_locked'

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Breno Leitao says:

====================
trace: add tracepoint for tcp_sendmsg_locked()

Meta has been using BPF programs to monitor tcp_sendmsg() for years,
indicating significant interest in observing this important
functionality. Adding a proper tracepoint provides a stable API for all
users who need visibility into TCP message transmission.

David Ahern is using a similar functionality with a custom patch[1]. So,
this means we have more than a single use case for this request, and it
might be a good idea to have such feature upstream.

Link: https://lore.kernel.org/all/70168c8f-bf52-4279-b4c4-be64527aa1ac@kernel.org/ [1]

v2: https://lore.kernel.org/20250407-tcpsendmsg-v2-0-9f0ea843ef99@debian.org
v1: https://lore.kernel.org/20250224-tcpsendmsg-v1-1-bac043c59cc8@debian.org
====================

Link: https://patch.msgid.link/20250408-tcpsendmsg-v3-0-208b87064c28@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2025-04-10 18:34:08 -07:00
commit 8127837aae
4 changed files with 28 additions and 1 deletions
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2
include/linux/socket.h
View File

@ -168,7 +168,7 @@ static inline struct cmsghdr * cmsg_nxthdr (struct msghdr *__msg, struct cmsghdr
return __cmsg_nxthdr(__msg->msg_control, __msg->msg_controllen, __cmsg);
}
static inline size_t msg_data_left(struct msghdr *msg)
static inline size_t msg_data_left(const struct msghdr *msg)
{
return iov_iter_count(&msg->msg_iter);
}

24
include/trace/events/tcp.h
View File

@ -259,6 +259,30 @@ TRACE_EVENT(tcp_retransmit_synack,
__entry->saddr_v6, __entry->daddr_v6)
);
TRACE_EVENT(tcp_sendmsg_locked,
TP_PROTO(const struct sock *sk, const struct msghdr *msg,
const struct sk_buff *skb, int size_goal),
TP_ARGS(sk, msg, skb, size_goal),
TP_STRUCT__entry(
__field(const void *, skb_addr)
__field(int, skb_len)
__field(int, msg_left)
__field(int, size_goal)
),
TP_fast_assign(
__entry->skb_addr = skb;
__entry->skb_len = skb ? skb->len : 0;
__entry->msg_left = msg_data_left(msg);
__entry->size_goal = size_goal;
),
TP_printk("skb_addr %p skb_len %d msg_left %d size_goal %d",
__entry->skb_addr, __entry->skb_len, __entry->msg_left,
__entry->size_goal));
DECLARE_TRACE(tcp_cwnd_reduction_tp,
TP_PROTO(const struct sock *sk, int newly_acked_sacked,
int newly_lost, int flag),

1
kernel/bpf/btf.c
View File

@ -6541,6 +6541,7 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = {
{ "xprt_put_cong", 0x10 },
/* tcp */
{ "tcp_send_reset", 0x11 },
{ "tcp_sendmsg_locked", 0x100 },
/* tegra_apb_dma */
{ "tegra_dma_tx_status", 0x100 },
/* timer_migration */

2
net/ipv4/tcp.c
View File

@ -1160,6 +1160,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
if (skb)
copy = size_goal - skb->len;
trace_tcp_sendmsg_locked(sk, msg, skb, size_goal);
if (copy <= 0 || !tcp_skb_can_collapse_to(skb)) {
bool first_skb;